On-line services networks commonly provide end users with access to a variety of different types of content entities. These content entities may include, for example, executable programs that can be downloaded to the user's computer, communications services (such as chat and email services) that allow users to communicate with one another, bulletin board system (BBS) services that allow users to review postings on various topics, and publications services that provide users with access to old and new printed publications. The various content entities are typically made available to users via a network directory system which presents users with a hierarchical view of the networks content.
In copending U.S. application Ser. No. 08/472,807 having the title ARCHITECTURE FOR SCALABLE ON-LINE SERVICES NETWORK, filed Jun. 7, 1995, there is described an on-line services network architecture in which the various user-accessible content entities are distributed on a number of different servers of a network. For example, one group of servers runs a BBS service application (and stores all BBS postings), while another group of servers runs a Chat service. Various benefits are realized by this architecture over conventional, mainframe designs. For example, the network can easily be scaled in size to accommodate increased numbers of users.
The present invention is directed generally to the problem of providing an extensible directory service for a distributed on-line services network, such as a network of the type described in the above-referenced application. One goal of the invention is to provide users with a hierarchical view of a distributed network's content such that the distribution of content entities among different servers is not apparent to the end user. Another goal is to provide a directory that is seen by users as a single, homogeneous is directory, rather than a collection of separate directories. Another goal is to provide a directory service that operates efficiently over a low-bandwidth communications channel, so that users do not experience significant delays while accessing the directory service over a wide area network. Another goal is to provide each user with a directory that is tailored to that user's particular access rights on the network. Another goal is to provide a directory service that is highly extensible, so that new content entities and entity types can easily be added as the network evolves. Another goal is to provide a directory service that is highly scalable in both content capacity and user capacity.